Smokeless ashless signal flare composition containing ammonium perchlorate



United States Patent 3,262,824 SMOKELESS ASHLESS SIGNAL FLARE COM- POSITION CONTAINING AMMONIUM PER- CHLORATE James B. McGrifiin, Linton, and William L. Ripley, Bedford, Ind., assignors to the United States of America as represented by the Secretary of the Navy No Drawing. Filed July 27, 1964, Ser. No. 385,518 4 Claims. (Cl. 149-42) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to an ashless signal flare composition and more particularly to an ashless signal flare composition which, when burned, emits a blue flame.

Various formulas have heretofore been used in compounding flares for military operations. Generally, those flares that produce a blue flame contain lead arsenate, and also may contain powdered metal, such as finely divided magnesium. While the use of magnesium in a blue flame formula may increase the candle power output of a flare, a dense white smoke is produced along with ash. This smoke tends to obscure the flame, and the ash causes the flare composition to burn unevenly. The use of lead arsenate causes the smoke and fumes to be a health hazard.

In the present invention an oxidizer-fuel system is used that is almost completely ashless and is comprised of a mixture of ammonium perchlorate and stearic acid. The ammonium perchlorate possesses the property of burning evenly, cool, and with only a small amount of smoke. As the mixture, upon burning, is practically ashless, all the heat formed is working heat, that is, as there is no residue left behind to absorb and hold heat, all the heat is dissipated out of the nozzle of the flare to increase the candlepower output and the color emission. In order to provide a blue color, a small amount of copper dust is added to the mixture of ammonium perchlorate and stearic acid.

It is therefor a general object of the present invention to provide an improved signal fiare for military operations.

Another object of the present invention is to provide a signal flare composition which, when burned, is ashless and emits a blue flame.

Other objects and advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description.

In manufactuiing a flare according to the teachings of the presentinvention, stearic acid and paraffin are melted together by heating at a temperature of about 90 degrees C. and copper dust is then added and mixed therewith. The melt is then cooled and screened and then mixed with the ammonium perchlorate. Satisfactory flares have been made by using between about 7080 percent, by weight, of ammonium perchlorate, between about 8-12 percent, by weight, of stearic acid, between about 1-4 percent, by weight, of paraflin, and between about 8-12 percent, by weight, of copper dust. The paraffin is used to desensitize the mixture to impact.

While the above-listed range of ingredients, when mixed, result in satisfactory flares, the following was found to be the optimum formula:

Various test flares were manufactured using the abovelisted optimum formula with the composition being pressed at a pressure of about 8000 p.s.i. A three-quarter inch diameter flare burned at a rate of 20 seconds per inch.- The ignition temperature was found to be about 250 degrees C. and the flares were relatively insensitive to both an electrostatic charge and to impact. As to electrostatic sensitivity, a charge of 4250 volts at a capacitance of 0.2 ,ufd. was applied to a test flare and no fire resulted.

In order to test impact sensitivity, a 100 mg. sample was placed on an iron block and a 2 kg. weight was dropped from various heights directly onto the sample.

-When the weight was dropped from a height of 41- cm.,

or more, the sample would fire. A sample is considered to be sensitive if there is a firing upon a drop of 20 cm. or less.

Visibility tests were performed in the field during daylight and were the subjective reports of observers. At a distance of 1000 yards, upon burning, both light and the blue color from the test flares were visible. At a distance of 1500 yards, light was visible but color was not visible.

The advantages of an ashless and smokeless signal flare composition for military use becomes readily apparent. There is no smoke to obscure the light or color of the flare nor is there any ash to absorb heat, obstruct the nozzle throat, or interfere with the smooth burning rate Within the flare body. Also with an ashless formulation there is a free dissipation of heat during the burning period and there is no extreme heating of the flare container.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. For example, as the color of the flare depends upon the particular molecular emitter used, it is entirely feasible that strontium or lithium compounds could be used instead of the copper dust when a red color is desired. Sodium compounds could be employed for a yellow color and barium or boron compounds could be employed for a green color. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed isr 1. A consumable pyrotechnic mixture consisting of between about and about ammonium perchlorate,

between about 8% and about 12% stearic acid,

between about 1% and about 4% of a desensitizing ingredient, and

between about 8% and about 12% emitter for producing color.

2. A consumable pyrotechnic mixture as set forth in claim 1 wherein said desensitizing ingredient is paraflin.

of a molecular 3. A. consumable pyrotechnic mixture as set forth in claim 1 wherein said molecular emitter is copper dust. 4. A consumablepyrotechnic mixture consisting of UNITED STATES PATENTS 8/ 1955 Heiskell 149-44 X 12/1955 Heiskell 149-44 References Cited by the Applicant UNITED STATES PATENTS Minrath.

Vinton.

Loedding.

Hall.

Brock.

Rolle et a1.

LEON D. ROSDOL, Primary Examiner.

B. R. PADGETT, Assistant Examiner. 

4. A CONSUMABLE PYROTECHNIC MIXTURE CONSISTING OF ABOUT 74.2%, BY WEIGHT, OF AMMONIUM PERCHLORATE, ABOUT 11.1%, BY WEIGHT, OF STEARIC ACID, ABOUT 3.6%, BY WEIGHT, OF PARAFFIN, AND ABOUT 11.1%, BY EIGHT, OF COPPER DUST. 